In a medium bowl, whisk together flour, baking powder, baking soda and salt. In large bowl with mixer, beat butter, sugar and extract at medium speed until light and fluffy. Beat in egg whites and whole eggs until smooth. With mixer on low, alternately beat in flour mixture and buttermilk until incorporated. Continue to beat batter on medium speed for 3 minutes. Divide batter between prepared pans.

Purée strawberries and syrup in blender; scrape through a fine sieve into a small saucepan to remove seeds. Bring mixture to a boil. Reduce heat to low; simmer until reduced to 1/3 cup, about 8 minutes. Cool completely.

In saucepan, bring 1 cup of the sugar and the water to a boil over high heat, stirring to dissolve sugar. Boil, without stirring, until syrup reaches 240ºF on a candy thermometer, about 5 minutes.

In a large bowl, beat egg whites and cream of tartar with mixer on medium speed until soft peaks form. Gradually add the remaining 1/4 cup sugar and beat until stiff peaks form. Gradually pour in boiling syrup in a thin stream. Increase mixer speed to high and beat until meringue is very thick and glossy, and completely cool, about 6 minutes.

Meanwhile, in a large bowl, combine butter, strawberry purée and food color, and vigorously beat with a rubber spatula until well combined and smooth. Fold in meringue, in two additions, until combined. Refrigerate buttercream 1 hour or until spreadable.

Using a serrated knife, halve cake layers horizontally. Place 1 layer, cut-side up, on a serving plate; spread with 2/3 cup buttercream. Arrange 1/3 of the diced strawberries in a layer over buttercream. Spread 2 Tbsp jam on a cut side of second layer and place, jam-side down, over strawberries. Repeat with remaining cake layers. Cover cake with buttercream. Pipe buttercream "kisses" on top if desired.

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